(1) Field of the Invention
The present invention relates to a display driving apparatus, a display module package, a display panel module, and a television set. The present invention relates in particular to the display driving apparatus that outputs n drive signals each of which drives a panel electrode, to n display output terminals in a predetermined cycle according to display data for a single line including n pixel data.
(2) Description of the Related Art
In recent years, a plasma display panel (PDP) has been attracting attention as a high-definition display panel having a flat large screen. The PDP is provided with, as pixels, discharge cells arranged in a matrix. The PDP displays an image using emission of light resulting from electric discharge of the discharge cells.
A PDP of a general AC-type includes display electrodes arranged parallel to one another and data electrodes arranged perpendicular to the display electrodes. A display driving apparatus of the PDP drives the data electrodes, which means a drive-target of the display driving apparatus is a capacitive load.
Along with advancements in the PDP, such as a larger screen, a higher definition, and a higher luminance, a display driving apparatus that drives the PDP has also been required to achieve a multi-output, a lower electromagnetic interference (EMI), and lower power consumption. Therefore, it has been becoming more important to suppress power consumption when driving a data electrode and resultant heat of driving, and reduce an EMI noise resulting from a change of data.
When different potentials are applied to two data electrodes, the electrodes function as a capacitance. In other words, a capacitive load is generated. The display driving apparatus consumes a lot of power when driving the capacitive load. In order to address the above, a display driving apparatus disclosed by Patent Reference 1: U.S. Pat. No. 7,116,137 is known as a conventional technique for reducing power consumption of the display driving apparatus.
The display driving apparatus according to the Patent Reference 1 converts display data to a predetermined voltage level and outputs the converted display data to a display output terminal connected to a data electrode. The display driving apparatus according to the Patent Reference 1 can reduce driving power with a two-step voltage driving method.
The display driving apparatus according to the Patent Reference 1 includes a common floating potential line connected to plural display output terminals in a floating state via a selection switch in a form of wired OR connection.
The display driving apparatus according to the Patent Reference 1 detects a change in a voltage level prior to and subsequent to a change of the display data. The display driving apparatus according to the Patent Reference 1 controls: the display output terminal of which the voltage level changes to temporarily enter a high-impedance (Hi-Z) state, with a predetermined timing (within a panel-nondisplay period for switching the display data); and at the same time, the selection switch so that the display output terminal is connected to the floating potential line. The control causes all of the display output terminals where data changes depending on the switching of the display data to have temporarily blocked display output and connected to the common floating potential line.
Accordingly, the display output terminal of which the voltage level changes is short-circuited, so that capacitive charge accumulated between the display output terminals to which an H (High) level or an L (Low) level is outputted immediately before is moved. This allows the display output terminal of the H level and the display output terminal of the L level to be balanced in number, causing the common floating potential line in a floating state to stay at a certain potential.
For example, in the display output terminals of which the voltage level changes, when the H level display output terminal and the L level display output terminal are the same in number, the common floating potential line ideally becomes VDD/2 (VDD is the H level potential of the display output terminal). Therefore, it is sufficient for the display driving apparatus to drive from VDD/2 to GND or to VDD. With this, the display driving apparatus according to the Patent Reference 1 can reduce driving power consumption.
Further, a conventional technique that reduces the EMI when display data changes is disclosed by Patent Reference 2: Japanese Patent No. 2953342.
In the technique disclosed by the Patent Reference 2, plural data electrodes that display pixel data for a single line is divided into plural sets of data electrodes, and a timing for a display output is sequentially shifted between the sets of data electrodes. With this, the technique disclosed by the Patent Reference 2 can group the number of data that changes at the same time into set units, thereby reducing a current peak. According to the above, the technique disclosed by the Patent Reference 2 can reduce the EMI that occurs.
However, with the display driving apparatus of the Patent Reference 1, the potential of the common floating potential line changes depending on a pattern of display data. For example, in the case where all of the output terminals change from the H level to the L level when switching the display data, the display driving apparatus disclosed by the Patent Reference 1 cannot reduce power consumption. More specifically, the display driving apparatus disclosed by the Patent Reference 1 depends on a pattern of the display data and in some cases cannot sufficiently reduce power consumption.
Further, although the display driving apparatus disclosed by the Patent Reference 2 can suppress the EMI by reducing the peak current, power consumption is not reduced. Further, the EMI is preferably reduced more than the reduction by the display driving apparatus disclosed by the Patent Reference 2.